Die assembly and method of using same

ABSTRACT

A die assembly suitable for spinning filaments and more particularly to a die assembly having a fluid environment around the die assembly&#39;s filament exit holes is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/233,990 filed Aug. 14, 2009.

FIELD OF THE INVENTION

The present invention relates to a die assembly suitable for spinningfilaments and more particularly to a die assembly comprising a fluidenvironment around the die assembly's filament exit holes.

BACKGROUND OF THE INVENTION

Die assemblies are known in the art. However, known die assemblies failto define a controlled fluid environment around their filament exitholes. As a result, the die assemblies exhibit negatives with respect tothe properties of the filaments formed by the die assemblies and/or thenumber of filaments capable of being made by the die assemblies.

Accordingly, there is a need for a die assembly that overcomes thenegatives associated with filaments formed from die assemblies and/orthe number of filaments capable of being formed by a die assembly.

SUMMARY OF THE INVENTION

The present invention fulfills the need described above by providing adie assembly that makes filaments that overcome the negatives associatedwith filaments formed from known die assemblies and/or the number offilaments capable of being formed by a die assembly.

In one example of the present invention, a die assembly comprising anozzle plate comprising a plurality of filament forming nozzlescomprising filament exit holes from which filaments exit the filamentforming nozzles during operation and wherein the die assembly furthercomprises an enclosure plate that defines an open area around thefilament forming nozzles, is provided.

In another example of the present invention, a die assembly comprising anozzle plate comprising a plurality of filament forming nozzles whereinthe filament forming nozzles comprise filament exit holes from whichfilaments are capable of exiting the filament forming nozzles duringoperation and wherein the die assembly defines a fluid environment influid contact with the filament exit holes that maintains greater than85% of the effective jet width of the fluid environment across thefilament exit holes, as measured according to the % Effective Jet WidthTest Method described herein, during operation of the die assembly, isprovided.

In another example of the present invention, a method for formingfilaments, the method comprising producing filaments from a die assemblycomprising a nozzle plate comprising a plurality of filament formingnozzles wherein the filament forming nozzles comprise filament exitholes from which filaments exit the filament forming nozzles duringoperation and wherein the die assembly further comprises an enclosureplate that defines an open area around the filament forming nozzles, isprovided.

In yet another example of the present invention, a method for formingfilaments, the method comprising producing filaments from a die assemblycomprising a nozzle plate comprising a plurality of filament formingnozzles wherein the filament forming nozzles comprise filament exitholes from which filaments exit the filament forming nozzles duringoperation and wherein the die assembly defines a fluid environment influid contact with the filament exit holes that maintains greater than85% of the effective jet width of the fluid environment across thefilament exit holes, as measured according to the % Effective Jet WidthTest Method described herein, during operation of the die assembly, isprovided.

Accordingly, the present invention provides a die assembly suitable forspinning filaments from a polymer melt composition that overcomes thenegatives associated with known die assemblies and a method for spinningfilaments from such a die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, perspective view of an example of a die assemblyin accordance with the present invention;

FIG. 2 is a cross-sectional view of the die assembly of FIG. 1 takenalong line 2-2;

FIG. 3 is a normalized temperature profile graph showing the normalizedtemperature profile of a die assembly according to the present inventioncompared to a prior art die assembly;

FIG. 4 is a schematic representation of a partial section view ofcomponents of an example of a die assembly according to the presentinvention;

FIG. 5 is a top plan view of an example of a die assembly according tothe present invention;

FIG. 6 is a top plan view of another example of a die assembly accordingto the present invention.

DETAILED DESCRIPTION OF THE INVENTION Die Assembly

The die assembly and method of the present invention are suitable forproducing filaments and products including such filaments, such as websand/or fibrous structures. The die assembly and method of the presentinvention may be used to produce different types of filaments, includingmelt-blown fibers, dry spun fibers and/or wet spun fibers. However, thedie assembly and method are particularly suited for producing filamentsfrom solvent, such as water, containing polymer melt compositions. Thepolymer materials suitable for use in the solvent containing polymermelt compositions include materials that are made flowable bydispersing, suspending and/or dissolving the material in a solvent.

In one example, the die assembly and method of the present invention arewell suited for materials that are solvent-soluble, and thus dissolvedin a solvent, such as water, prior to being forced through the filamentforming holes to form filaments. Often it is desirable to attenuate, orstretch, the filaments exiting the filament exit holes of the dieassembly.

The die assembly of the present invention comprises one or more filamentforming nozzles comprising one or more filament exit holes from whichfilaments are capable of exiting the filament forming nozzles duringoperation and wherein the die assembly defines a fluid environment influid contact with the one or more filament exit holes that maintainsgreater than 85% and/or greater than 87% and/or greater than 89% to lessthan 99% and/or less than 95% and/or less than 91% of the effective jetwidth of the fluid environment across the one or more filament exitholes, as measured according to the % Effective Jet Width Test Methoddescribed herein, during operation of the die assembly.

As shown in FIGS. 1 and 2, an example of a die assembly 10 in accordancewith the present invention comprises a nozzle plate 12 comprising one ormore filament forming nozzles 14. The filament forming nozzles 14comprise filament exit holes 16. The die assembly 10 defines a fluidenvironment 18 in fluid contact with the filament exit holes 16 of thefilament forming nozzles 14. The fluid environment 18 maintains greaterthan 85% of the effective jet width of the fluid environment across thefilament exit holes 16 of the filament forming nozzles 14, as measuredby the % Effective Jet Width Test Method, during operation of the dieassembly 10.

The die assembly 10 may be designed to supply both the material fromwhich filaments are formed and an attenuation medium (such as air, gasor other fluid) for attenuating the filaments as they exit the filamentexit holes 16 of the filament forming nozzles 14. The die assembly 10may be in fluid communication with one or more material sources, such asa polymer source, that supplies the material from which filaments areformed to the filament forming nozzles 14. The die assembly 10 mayinclude at least one attenuation medium inlet 20 through which anattenuation medium may enter the die assembly 10. The attenuation mediuminlet 20 may be in fluid communication with a fluid source, such as asource of air, gas or other fluid that is used as an attenuation mediumwhen forming the filaments. The die assembly 10 further comprises anattenuation medium exit 22, which is the location at which theattenuation medium exits the die assembly 10.

The die assembly 10 may further comprise an enclosure plate 24. Theenclosure plate 24 comprises an open area 26 into which the filamentforming nozzles 14 extend. One or more of the filament forming nozzles14 may extend completely through the open area 26. One or more of thefilament forming nozzles 14 may be flush with a surface of the enclosureplate 24. One or more of the filament forming nozzles 14 may extend lessthan completely through the open area 26. The open area 26 comprises thefluid environment 18 that is in contact with the filament exit holes 16.The enclosure plate 24 may direct fluid, such as air, toward thefilament exit holes 16. In one example, the enclosure plate 24 directs afluid into the open area 26 comprising the fluid environment 18 at anangle of greater than 30° and/or greater than 45° and/or greater than60° and/or to about 90° to the fluid environment 18.

The open area 26 may be of any shape so long as the filament formingnozzles 14 are in contact with the fluid environment 18.

The enclosure plate 24 further comprises an exterior surface 28 and aninterior surface 30. The exterior surface 28 is exposed to the externalenvironment. The interior surface 30 is positioned inwardly into the dieassembly 10 towards the nozzle plate 12. The interior surface 30 definesa cavity 32 between the interior surface 30 and an air plate 34 withinthe die assembly 10. The cavity 32 is capable of receiving fluid, suchas air, and directing it to the open area 26. In one example, the cavity32 comprises one or more external environment openings, other than theopen area 26, through which a fluid may enter the cavity 32 from theexternal environment and be directed to the open area 26.

The die assembly 10 may further comprise an air plate 34 as shown inFIGS. 1 and 2. The air plate 34 is positioned between the nozzle plate12 and the enclosure plate 24. The air plate 34 comprises filamentforming nozzle receiving holes 36 through which one or more of thefilament forming nozzles 14 extend. At least one of the filament formingnozzle receiving holes 36 are sized such that an attenuation medium mayalso pass through the filament forming nozzle receiving hole 36 on itsway from the attenuation medium inlet 20 to the attenuation medium exit22.

In one example, the filament forming nozzle receiving holes 36 arealigned with the open area 26 such that the attenuation medium exits thefilament forming nozzle receiving holes 36 into the open area 26.

In another example, the air plate 34 may further comprise one or morefirst air holes 38, void of a filament forming nozzle 14, but adjacentto one or more filament forming nozzle receiving holes 36. In oneexample, the first air holes 38 are positioned between one or morefilament forming nozzle receiving holes 36 and an edge 40 of the airplate 34.

In one example, as shown in FIGS. 3 and 4, the filament forming nozzlereceiving holes 36 and the first air holes 38 are positioned within theopen area 26. In one example, the open area 26 comprises a first gap W1that defines a minimum distance between an edge of a first air hole 38to an edge of the enclosure plate 24. In one example, the first gap W1is less than 0.020 mm and/or less than 0.018 mm and/or less than 0.015mm and/or less than 0.010 mm and/or less than 0.008 mm.

In another example, the open area 26 comprises a second gap W2 thatdefines a minimum distance between an edge of a first air hole 38 to anedge of the enclosure plate 24. In one example, the second gap W2 may bethe same or different from the first gap W1. In another example, thesecond gap W2 is less than 0.020 mm and/or less than 0.018 mm and/orless than 0.015 mm and/or less than 0.010 mm and/or less than 0.008 mm.

Two or more of the first air holes 38 may exhibit the same or differentdiameters.

In still another example, the enclosure plate 24 may comprise paralleledges that define the open area 26. In yet another example, theenclosure plate 24 at least one edge that defines a boundary of the openarea 26 that converges toward the filament exit holes 16 of the filamentforming nozzles 14. In even yet another example, the enclosure plate 24may comprise at least one edge that defines a boundary of the open area26 that diverges away from the filament exit holes 16 of the filamentforming nozzles 14.

In another example, the air plate 34 may comprise one or more second airholes 42, void of a filament forming nozzle 14, through which anattenuation medium may pass. The one or more second air holes 38 may bealigned with the cavity 32. The cavity 32 is capable of directing theattenuation medium from the second air holes 42 into the open area 26 asshown by the arrows. The attenuation medium from the second air holes 42combines with the attenuation medium from the filament forming nozzlereceiving holes 36 to form the fluid environment 18 during operation ofthe die assembly 10.

Two or more of the second air holes may exhibit the same or differentdiameters.

The arrows shown in FIG. 2 exemplify one or more attenuation medium flowpaths through the die assembly 10 during operation of the die assembly10.

The filament forming nozzles 14 may be formed from small metal tubeshaving generally circular cross-sections. Alternatively, the filamentexit hole 16 of any particular filament forming nozzle 14 may have anycross-sectional shape, may have varying inner and/or outer effectivediameters, may be tapered (e.g. the downstream outer effective diameteris less than the upstream outer effective diameter) or beveled and maybe made from any suitable material. The filament forming nozzles 14 mayall have the same upstream inner and/or outer effective diameter or mayhave different upstream inner and/or outer upstream effective diameters.Likewise, the filament forming nozzles 14 may all have the samedownstream inner and/or outer effective diameter or may have differentupstream inner and/or outer downstream effective diameters. Further, thefilament forming nozzles 14 may be the same length or may be differentlengths and/or may be mounted so as to extend from the nozzle plate 12different amounts. The filament forming nozzles 14 may be made from aseparate material that is mounted or otherwise joined to the nozzleplate 12 or may be formed in the material making up the nozzle plate 12itself. The filament forming nozzles 14 may be permanently mounted tothe nozzle plate 12 or may be removable and/or replaceable. Exemplarymethods for mounting filament forming nozzles 14 in the nozzle plate 12include, but are not limited to, laser welding, soldering, gluing,pressure fitting and brazing.

In one example of the present invention, as shown in FIGS. 1 and 2, thefilament forming nozzles 14 are disposed in multiple adjacent rows,wherein each row includes a multiplicity of filament forming nozzles 14.Although FIGS. 1 and 2 show the filament forming nozzles 14 disposed inregular rows with equal numbers of filament forming nozzles 14 in eachrow, any suitable number of filament forming nozzles 14 may be in anyparticular row.

As shown, for example, in FIGS. 1 and 2, the die assembly 10 of thepresent invention may also include a spacer plate 44 positioned betweenthe nozzle plate 12 and the air plate 34. The spacer plate 44 functionsto direct the attenuation medium in a direction generally parallel tothe filament forming nozzles 14 and to promote flow uniformity, asdesired, throughout the attenuation area surrounding the filamentforming nozzles 14. As such, the spacer plate 44 has a spacer plateopening 46 through which at least some of the filament forming nozzles14 may extend.

Even though FIGS. 1 and 2 shows the die assembly 10 being made fromindividual components, the die assembly 10 may be a single piece.

Method for Forming Filaments

As discussed above, the die assembly of the present invention issuitable for forming filaments from materials, especially polymermaterials.

In one example of the present invention, a method for forming filamentscomprises the steps of producing filaments from a die assemblycomprising a nozzle plate comprising a plurality of filament formingnozzles wherein the filament forming nozzles comprise filament exitholes from which filaments exit the filament forming nozzle duringoperation and wherein the die assembly defines a fluid environment influid contact with the filament exit holes that maintains greater than85% of the effective jet width of the fluid environment across thefilament exit holes, as measured according to the % Effective Jet WidthTest Method, during operation of the die assembly.

The die assembly may comprise a material source that is in fluidcommunication with the filament forming nozzles such that the amaterial, for example a polymer material such as starch, is able to bepassed through the filament forming nozzles and exit the filament exitholes to as filaments.

As the filaments are exiting the filament exit holes, the filaments arein fluid contact with the fluid environment.

The filaments may be subjected to attenuation by an attenuation medium,such as air, that contacts the filaments and attenuates the filaments asthe filaments move downstream of the filament exit holes.

The filaments produced by the die assembly may be collected on acollection device, such as a belt or fabric, which may be patterned, toproduce a web or fibrous structure.

Test Methods

Unless otherwise specified, all tests described herein including thosedescribed under the Definitions section and the following test methodsare conducted on samples that have been conditioned in a conditionedroom at a temperature of 73° F.±4° F. (about 23° C.±2.2° C.) and arelative humidity of 50%±10% for 2 hours prior to the test. All testsare conducted in such conditioned room.

% Effective Jet Width Test Method

The % effective jet width is determined by measuring the normalizedtemperature profile of the fluid environment across the filament formingexit holes of the filament forming nozzles of a die assembly.

A thermocouple probe (1.6 mm diameter) is mounted on a motorizedtraverse (Dantec systems, used with their Laser Doppler equipment). Thethermocouple is mounted such that the tip can approach the die assemblyfrom downstream to upstream; angling into the fluid environment in fluidcontact with the filament exit holes of the filament forming nozzles ofthe die assembly. The traverse is used to position the tip of thethermocouple downstream of the die assembly and enclosure plate by 1.6mm.

As shown in FIG. 5, the probe is centered along the narrow, minor axisA_(M) of the fluid environment 18 in the open area 26, which is in fluidcontact with the filament exit holes 16 of the filament forming nozzlesof the die assembly 10, and defines a zero position. The probe should beat least 5 cm away from the die assembly edges along the longer, majoraxis A_(R) of the fluid environment 18 in the open area 26. The traverseis used to move the probe across the narrow, minor axis A_(M) of thefluid environment 18 on 1 mm spacings, far enough that the surroundingtemperature can be measured along with the main fluid environment'stemperature.

The resulting temperature data is resealed to yield a normalizedtemperature profile. The maximum and minimum temperature for the datasetis determined. For each temperature measurement at position x, anormalized temperature is calculated.

If the maximum temperature corresponds to the fluid environmenttemperature then the normalization formula is as follows:

${TNormal}_{X} = \frac{T_{X} - T_{\min}}{T_{\max} - T_{\min}}$

If the minimum temperature corresponds to the fluid environmenttemperature, then the normalization formula is

${TNormal}_{X} = \frac{T_{\max} - T_{X}}{T_{\max} - T_{\min}}$

The normalized temperature data is then plotted with the probe position(x) shown on the abscissa and the normalized temperature shown on theordinate. The effective jet width of the fluid environment is thendetermined graphically by determining the two points where the fluidenvironment achieves 90% of the normalized temperature, an example ofsuch as graph is shown in FIG. 6, which shows a normalized temperatureprofile for both a die assembly outside the scope of the presentinvention labeled “No Enclosure” and a die assembly within the scope ofthe present invention, labeled “With Enclosure”. The width is then thedifference in abscissa positions between these two 90% points.

Once the width is determined, then the % effective jet width isdetermined

${\% \mspace{14mu} {EffectiveJetWidth}} = {100 \times \frac{EffectiveJetWidth}{AirPlateWidth}}$

The air plate width is defined as the width between the outermost edgeof the outermost holes in the air plate, lying along the minor axis ofthe air plate. The resulting value is the value that is reported as the% Effective Jet Width value that the fluid environment maintains acrossthe filament exit holes of the filament forming nozzles.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

1. A die assembly comprising a nozzle plate comprising a plurality offilament forming nozzles, wherein the filament forming nozzles comprisefilament exit holes from which filaments exit the filament formingnozzles during operation, wherein the die assembly further comprises anenclosure plate that defines an open area around the filament exit holesof the filament forming nozzles.
 2. The die assembly according to claim1 wherein the open area defines a fluid environment around the filamentexit holes of the filament forming nozzles.
 3. The die assemblyaccording to claim 1 wherein the enclosure plate comprises at least oneedge that defines a boundary of the open area that converges toward thefilament exit holes of the filament forming nozzles.
 4. The die assemblyaccording to claim 1 wherein the enclosure plate defines a cavity thatis positioned between the enclosure plate and the nozzle plate.
 5. Thedie assembly according to claim 4 wherein the cavity is in fluidcommunication with the open area.
 6. The die assembly according to claim5 wherein the cavity is capable of receiving a fluid and directing thefluid to the open area.
 7. The die assembly according to claim 6 whereinthe fluid comprises air.
 8. The die assembly according to claim 1wherein the die assembly further comprises an air plate positionedbetween the enclosure plate and the nozzle plate, wherein the air platecomprises a plurality of holes through which one or more filamentforming nozzles extend.
 9. The die assembly according to claim 8 whereinthe air plate further comprises one or more holes that are void offilament forming nozzles.
 10. A die assembly comprising a nozzle platecomprising a nozzle plate comprising a plurality of filament formingnozzles wherein the filament forming nozzles comprise filament exitholes from which filaments are capable of exiting the filament formingnozzles during operation and wherein the die assembly defines a fluidenvironment in fluid contact with the filament exit holes that maintainsgreater than 85% of the effective jet width of the fluid environmentacross the filament exit holes, as measured according to the % EffectiveJet Width Test Method, during operation of the die assembly.
 11. The dieassembly according to claim 10 wherein the die assembly furthercomprises an enclosure plate that directs a fluid into the fluidenvironment.
 12. The die assembly according to claim 11 wherein theenclosure plate directs a fluid into the fluid environment at an angleof greater than 30° to the fluid environment.
 13. The die assemblyaccording to claim 11 wherein the enclosure plate comprises an open areathat receives the filament forming nozzles.
 14. The die assemblyaccording to claim 13 wherein the filament forming nozzles extendthrough the open area of the enclosure plate.
 15. The die assemblyaccording to claim 11 wherein the fluid comprises a gas.
 16. The dieassembly according to claim 15 wherein the gas comprises air.
 17. Thedie assembly according to claim 11 wherein the die assembly furthercomprises an air plate that is positioned between the enclosure plateand a nozzle plate comprising the filament forming nozzles.
 18. The dieassembly according to claim 17 wherein the air plate comprises filamentforming nozzle receiving holes that receive the filament forming nozzlesof the nozzle plate.
 19. The die assembly according to claim 17 whereinthe air plate comprises air holes void of filament forming nozzles. 20.A method for forming filaments, the method comprising the step ofproducing filaments from a die assembly comprising a nozzle platecomprising a plurality of filament forming nozzles wherein the filamentforming nozzles comprise filament exit holes from which filaments exitthe filament forming nozzle during operation and wherein the dieassembly defines a fluid environment in fluid contact with the filamentexit holes that maintains greater than 85% of the effective jet width ofthe fluid environment across the filament exit holes, as measuredaccording to the % Effective Jet Width Test Method, during operation ofthe die assembly.